Portable drug delivery devices are used for the administration of a drug that is suitable for self-administration by a patient. A drug delivery device is especially useful in the shape of a pen, which can be handled easily and kept everywhere available. A type of drug delivery device is constructed to be refillable and reusable many times. A drug is delivered by means of a drive mechanism, which may also serve to set the dose or amount to be delivered.
DE 102 37 258 B4 describes a drug delivery device in the shape of an injection pen having a drive mechanism, which allows to deliver a plurality of different prescribed doses. The drive mechanism comprises elements which are rotated relatively to one another around a common axis. They are coupled by unidirectional gears.
EP 0 498 737 A1 describes a mechanism of an injector comprising a plunger with a locking portion, a return preventive member with a locking portion, and a cartridge holder with a cartridge acting on a cartridge receiving member, which is biased by compression of a push spring. As long as the cartridge is attached, the locking portions of the plunger and the return preventive member are engaged by the action of the cartridge receiving member. When the cartridge is detached, the locking portions are disengaged.
EP 1 923 083 A1 describes a drive mechanism for use in drug delivery devices comprising a piston rod with first and second sets of indentations, a lever with a first pivot and a second pivot, and lugs of the lever, which are releaseably engaged with the first set of indentations and allow a force transmission to the piston rod during dispense and a relative movement between the lever and the piston rod during setting. A pawl means engaging the second set of indentations prevents the piston rod from moving while a dose is being set.